The manufacturers of automotive vehicles rely more and more on packaged components for the vehicles that they assemble. Whereas before, certain parts were installed separately along an assembly line, now many of these same parts are incorporated into components which are assembled elsewhere and installed on vehicles in considerably less time and with greater ease than were the individual parts. The hub assemblies by which the road wheels of a vehicle are attached to the suspension system of the vehicle provide a good example.
Not long ago, automotive manufacturers, when assembling a vehicle, would install a spindle as part of the front suspension system of a vehicle, then place an inboard bearing, a hub and an outboard bearing in that order around the spindle, followed by a nut threaded over the spindle and tightened against the outboard bearing just enough to give the two bearings the correct setting. Now a parts supplier furnishes a hub fitted to a housing with bearings located between the two and adjusted to the proper setting, that is to say, the parts supplier provides a preassembled hub/bearing assembly. The automotive manufacturer bolts the housing of the hub/bearing assembly to a suspension system component, and later attaches a brake disk and wheel to the hub.
Drive shafts complicate the procedure, and many vehicles have transverse shafts coupled to their front wheels, whether they be front wheel drive vehicles or four wheel drive vehicles. In this regard, the typical transverse shaft leads out to a constant velocity (CV) joint having an enlarged body or shell and a half-shaft projecting outwardly from the shell where it has a spline followed by a reduced end that is threaded. The spline mates with a corresponding spline in the hub of the hub/bearing assembly, while the thread on the reduced end is engaged with a nut that attaches the CV joint to the hub.
But the CV joint together with the transverse shaft to which it is coupled are quite heavy, weighing up to 50 lbs., and the hub/bearing assembly is heavy as well, making it difficult for an assembly line worker to manipulate and align the spline of the hub with the spline on the half-shaft. To be sure, the threaded end of the half-shaft fits easily into the larger splined bore of the hub, but does not align the two splines. The differences in diameter between the threaded end and the spline on the half-shaft together with the multiple degrees of freedom accorded to the half-shaft by the CV joint make it difficult and time consuming to bring the spline on the half-shaft into axial alignment with the spline in the hub—and, of course, the two splines cannot be engaged until they are so aligned.